Use of information technologies in hospital has gained increased attention due to their potential to enhance efficiency and hence reduce costs and increase access. Information systems research has found complex dynamics related to IT impacts. In this research we examine how different patterns in the IT Architecture of hospitals differently impact hospital efficiency. Specifically, we examine three facets of a hospitals IT architecture: IT Architecture Spread (ITAS), IT Architecture Longevity (ITAL), and IT Architecture Domain (ITAD). Two dimensions of a hospital’s IT Architecture are : IT Architecture Spread (ITAS), which refers to the breadth of digitization of hospital work processes, and IT Architecture Longevity (ITAL), which refers to the maturity of the technology portfolio implemented in a hospital. The impacts of these two dimensions are assessed across the two domains of hospitals work– clinical and business – which are referred to as IT architecture domain (ITAD). Besides the linear impacts of ITAS and ITAL we also examine their non-linear interactive impacts on hospital efficiency. Utilizing archival data on 287 Californian hospitals, our results demonstrate that the enterprise IT architectures in clinical and business domains may have significantly distinct effects on efficiency. More importantly, our research points to how the two dimensions of IT architecture can explain distinct pathways in the impacts of IT on the performance of healthcare firms.